The present disclosure relates, in general, to electronics, and more particularly, to circuits and method for providing power to electronic devices. Such circuits may use Synchronous Rectification (SR) circuits, in which an Alternating Current (AC) voltage is rectified using one or more switching devices, such as transistors, that are switched on and off synchronously with the AC voltage. The switching devices may be controlled by signals from an SR control circuit.
The SR control circuit may turn a switching device on and off in response to a voltage across the switching device or a current passing through the switching device. A first threshold, i.e., an on threshold, may be used when determining whether to turn the switching device on. A second threshold, i.e., an off threshold, may be used when determining whether to turn the switching device off.
Ringing on the voltage across the switching device way cause the voltage across the switching device to cross the on threshold at times when it would be inappropriate to turn on the switching device. The ringing may be present in a predictable period after the switching device is turned off. Accordingly, the SR control circuit may impose a minimum switching device turn-off time to prevent the ringing during the predicted period after the switching device is turned off from turning the switching device back on. However, the use of the minimum switching device turn-off time may interfere with the ability of the SR control circuit to operate at high frequencies or may require additional pins, components, or both to configure the minimum switching device turn-off time.
Accordingly, it is desirable to have SR control circuit that is able to prevent the ringing from turning on the switching device without the use of a minimum switching device turn-off time.
Those skilled in the field of the present disclosure will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of the embodiments.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments. This avoids obscuring the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the disclosures herein. The details of well-known elements, structures, or processes that are necessary to practice the embodiments and that are well known to those of skill in the art may not be shown and should be assumed present unless otherwise indicated.